CHICAGO — A new study suggests that boys in the United States, like girls, are entering puberty slightly earlier than previously thought, with blacks the most likely to develop the first signs by age 10.
Skeptics challenged the findings but said they raise important questions worthy of more comprehensive study.
Early puberty may increase a boy’s chances of developing testicular cancer later in life because it may mean longer exposure to sex hormones, said University of North Carolina researcher Marcia Herman-Giddens, the study’s lead author. If boys are truly maturing earlier, then sex education classes should begin earlier, she said.
The study, an analysis of a 1988-94 federally funded national health survey, found the average age for developing pubic hair was 12 in white boys, 11.2 years in blacks and 12.3 years for Mexican-Americans. That’s up to half a year earlier than in earlier studies, Herman-Giddens said.
But 21 percent of black youngsters studied had developed pubic hair between their 9th and 10th birthdays, compared with 4.3 percent of white boys and 3.3 percent of Mexican-Americans.
The study also suggests that a significant number of boys as young as 8 in all three races had signs of genital development — some three years earlier than previous estimates. But the authors and other experts say those signs likely are too subjective from which to draw conclusions.
On average, ages for the start of genital growth were 10 for white boys, 9.5 for blacks and 10.4 for Mexican-Americans.
The study appears in September’s Archives of Pediatrics &Adolescent Medicine. Herman-Giddens’ previous research, published four years ago, suggested that significant numbers of white and black girls begin to develop sexually by age 8.
Potential reasons for earlier development include rising obesity rates, better nutrition, exposure to environmental chemicals that can mimic sex hormones and use of infant formula and other products containing soy, which also can mimic sex hormones, Herman-Giddens said.
Genetics and environmental differences may explain racial disparities, she said.
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